Report on the Transport and Fate of Selected EDCs During the Land Application of Biosolids
Research Questions: Determine what are the major sources and environmental fates of EDCs natural and/or pharmaceutical additives. Determine how unreasonable risk can be managed. This research provides information to address a data gap in the research to identify major sources and environmental fate of EDCs. Biosolids may contain significant levels of EDCs and their fate once land applied has not been determined. This research will be used to evaluate existing risk management strategies for the disposal of biosolids and begin to evaluate alternative risk management options.
In the US, over 3 million dry tons of treated sewage sludge (or biosolids) are applied on agricultural lands. Recently, questions have arisen about the risks of this practice. There is concern that current practices are not sufficiently protective of pathogen and chemical exposures. Biosolids may contain significant quantities of steroid hormones, alkyl phenols, and other endocrine disrupting chemicals. Through land application, these chemicals may be introduced into the environment where they may impact surface and ground water, soil, and sediments. To evaluate these questions, the concentrations of pathogens, other microbes, nutrients, and EDCs will be measured before and after biosolids application to land. The persistence, transport, and fate of these analytes will be studied and when possible, kinetic rates will be calculated to characterize the system.
This research has been conducted in conjunction with water quality research on biosolids, and it is anticipated that this leveraging will continue throughout future research. This research is expected to have a laboratory and field component.
Accomplishments to Date: In 2004-2005, a field study measured the concentrations of contaminants of concern when an anaerobically digested biosolids were applied at agronomic levels. The concentrations of alkyl phenol ethoxylates and their degradation products, and the diversity and size of the microbial community by phospholipid fatty acid analysis (PLFA) were measured as well as other quantities of interest. Concentrations were measured before and after biosolids application at various soil depths and as a function of time. In addition, supporting information was also gathered such as temperature and weather data. Data analysis is on-going. Preliminary EDC conclusions are that alkyl phenols were found in the top layer of soil, they were not transported into the soil column, and they persisted longer than expected based on literature data.
Based on this data, future studies are needed to resolve uncertainties in rates, establish persistence and fate of steroid hormones, and determine the characteristics which affect the persistence and fate of EDCs in this situation. Important variables in these studies include: type and source of biosolids, application season and weather conditions, soil type, and operational variables in application. Both lab and field scale studies will be useful depending on the specific questions to be evaluated. Variability observed in the 2004-2005 study indicates that a more robust sampling plan is needed for future field studies. Results from the first study will be presented at the WEF Residuals and Biosolids Management Conference in March 2006. In addition, a paper will be submitted to WEF describing this study.
The regulations which govern the land application of biosolids were promulgated in 1993. Since that time, methods for treating and handling biosolids have evolved. In 2002, the National Research Council (NRC) advised that the regulations should be updated, including a determination if additional chemicals should be regulated. Based in part on this recommendation, EPA will evaluate current regulations and revise them as needed. Research on EDC persistence, transport, and fate following land application of biosolids will facilitate science-based decisions in these regulations.
Research projects within this theme will be completed at the laboratory and field scale such as reporting the occurrence of EDCs in soils following land application of biosolids and the fate of these compounds over time. These studies will be used to satisfy an APM reporting the transport and fate of selected EDCs during the land application of biosolids.
Users of this information will include the Office of Water as well as wastewater and CAFO operators.
Carolyn Acheson at email@example.com